Biocide.

If you want a plant killed off, contact myself and S. I'm merely the non-active accomplice, but S is a cold-hearted assassin.
Over the years, she has been given countless potted plants as presents, only for them to mysteriously go missing or to be found cold and limp on the floor. She's ruthless. Even the orchid, that we were told was impossible to kill off, I have found, this evening, twitching in the corner of the room.
So if you have in your possession a plant you don't like the look of, let us know and, with no questions asked, all your troubles will be over very quickly, my friend.